cold-weather oil for old 4-speed

[LCAM-01XA]

A friend from the Great White (and as of lately apparently ridiculously cold) North asked me this, and I wasn't sure what to tell them so I figured I'd run it by ya'll first:

The problem is that with their recent stupid-low temperatures 80w90 gear oil turns into such molasses that the transmission in question objects to any and all attempts of shifting before engine has warmed up properly, which this being a gasser does take a while. The question is, can the gear oil be replaced with engine oil, say 20w50? According to Novak's website the fullsize 4-speeds call for straight 50W oil from the factory. Most fulsize 5-speeds seem to run on Dex/Merc transmission fluid which IIRC has a viscosity of around 5W, so I can't see running 20W (the 20w50 while still cold) doing any damage to the 4-speed. To make things even more interesting Mopar does officially list 10w30 engine oil as replacement for the 75w90 gear oil initially required in their AX15 (small 5-speed) transmissions, the viscosity gap there is even larger yet the thin oil still works good. So this leads me to believe 20w50 engine oil would do fine in a 4-speed especially in cold weather. If so, detergent or non-detergent engine oil would be better?

What says the brotherhood?

 

[riotwarrior]

First what is the transmission in question.

If it requires EPL 80-90 then I'd suggest an EPL 75-140 FULL synthetic myself.

 

[Saskredneck]

I run 80w90 in both my 4 speeds without any issues in the cold, just don't shift it like a racecar when its cold it isn't too bad. Has been in the -40 to-60 range most the winter so far so unless he's more north of me and enjoying even colder temps I wouldn't worry. My truck runs minimal 20 minutes before I go anywhere when it gets cold, if its not getting up to temp before driving they need to warm truck up longer or install a high idle on the gas job. I did this to my 86 f150 & 94 f150 using manual choke cable to the throttle body to hold a higher rpm for quick warm ups.

 

[chris142]

I dont see why you cant run a multi vis oil in it till winters over. The gears will break the oil down but a few months will be ok. I ran sae30 in my t19 that called for sae50 for decades with no issues.

If i was you guys id throw 5w30 or 0 w 30 synthetic in it

 

[chris142]

Btw you do know that gear oils and motor oils are rated differently right? A 90wt gear oil is close to a 50 wt motor oil

 

[riotwarrior]

one more thing...if he has a 4wd stick the tcase in N and trans in 1 or R and let spin at idle for few minutes...to heat up and move around oil before taking off....ask how I know!

 

[FordGuy100]

Mine has 15w40 Amsoil in it, probably for the last 20K miles.

 

[LCAM-01XA]

Riot, one transmission is either a T18 or a NP435 (non-synchronized creeper 1st, so it could be either) and the other is most likely a SM465, both apparently have the "thou shalt not shift" attitude but the Ford one is worse. Good call on the idea of neutraling the t-case, that trick would work for both transmissions actually. And since you said to ask, how do you know?

Saskredneck, eek that is COLD!!! Not that bad where they are, think the lowest I've heard complaints about so far has been -30 or so. The high idle has been discussed and will be a project for when I go visit them, we'll probably just copy my setup with the vernier cable hooked up right to the throttle pedal (this eliminates running another cable thru the firewall and trying to figure out how to hook it up to the TB so that it doesn't interfere with the factory stuff), but till then I'd rather not have them attempt to conjure something on their own. Prolonged warmup times are not always possible tho, hence the need for high idle like you suggested and/or thinner oil.

Chris142, no I did not know the oils are rated differently - I thought all the numbers I see on the bottles are standard SAE numbers, thus 80-90 gear oil would be a whole lot thicker than straight-50 engine oil. Why do they rate them differently? That makes little sense to me, you can't compare nothing like that. Also, I was under the impression that engines break down additives faster than gears, so what only lasts a few thousand miles in an engine would generally last many times more in a transmission or axle. That said, if they do as you suggest and go with 5w30 synthetic oil, what would be the expected useful life of the oil - being synthetic and not subjected to corrosive action from combustion gases the additives should last quite a long time, right?

Justin, 15-40 was also a consideration, I meant to ask about it also but I forgot.

 

[FarmerFrank]

You could put mud in a granny low 4 speed and be fine.

I wouldn't think much about motor oil for winter. Gear oil keeps them quieter in the summer months. I'd venture to say ATF in it would work for a while.

 

[Dieselcrawler]

I to do the tcase in neutral trans in 2nd gear in my f100. the 3 on the tree really doesn't like the cold.

 

[chris142]

http://www.bobistheoilguy.com/viscosity-charts/ dunno why they are rated on a different scale but here it is....

 

[riotwarrior]

Riot, one transmission is either a T18 or a NP435 (non-synchronized creeper 1st, so it could be either) and the other is most likely a SM465, both apparently have the "thou shalt not shift" attitude but the Ford one is worse. Good call on the idea of neutraling the t-case, that trick would work for both transmissions actually. And since you said to ask, how do you know?

I know because I'm a C A N A D I A N and we do things a little differently and also that work in the cold. Dad had a F250 390 NP435/NP205 and when it was -40 it shifted like ***** and I'd have to go warm it up by doing what I said, this was back in 70's so I learned that trick many moons ago...It's a Canadian thing I guess I faced similar temps then as Saskredneck, is now

EPL lube is a different lube than engine oil, Extreme Pressure Lube aka gear oil, so hopefully checking on this will help.

EPL may still contain zinc additive I don't know, but there are different additive packages to an EPL than a SFI/CDI oil that much I do know.

 

[chris142]

When these old 4 speeds were designed the oil used was a gl1 gear oil. Basically a 90wt trans/50 wt oil with no anti wear addatives,just some anti foaming addatives. Todays 80/90 gl5 gear oils are not the correct oil as the aw addatives may destroy the soft parts. The closest thing made today to a gl1 gear oil is sae 50 engine oil.

Another option would be the synchromesh trans oils made today. Those are close to a 5w30

 

[Black dawg]

like said, synthetic gl will work way better, and the t case in neutral trans in gear trick works great.

 

[riotwarrior]

IIRC GL is an EPL lube 80-90 weight, I'm not 100% on this been many years since had to deal with this detail of lube issues. However GL or Gear Lube is an extreme pressure lube, as in the forces on Crown/Pinion etc are quite high and thus requirements are EPL GL but like said was over 30 years ago I was dealing with ***** like this for race car etc.

Al